As we continue to explore the Voyage, we come across the PagePress sensors. The sensors are held to the display assembly with some mild adhesive for good contact.

What exactly is PagePress? Glad you asked.

"PagePress is a custom-designed force sensor made of carbon and silver, which reacts to a subtle increase of pressure, triggers a page-turn, and provides a haptic response only your thumb can perceive."

Sounds like some kind of strain gauge implementation to us. A strain gauge is a component that changes resistivity when deformed, making for an excellent buttonless button.